Hannah Perner-Wilson put a small push button, battery holder, and LED/vibrating motor inside these little limpet shell. She writes:

I’ve always liked collecting seashells, and have always wanted to do something more with them than accumulate them in my parent’s garden. So now I want to see how far I can go to integrate small electronic circuits inside them. Limpits are nice to work with because they are totally open on one side and the bigger ones even offer some depth.

The limpit buttons are very simple, they use a push-button to trigger LED light or a vibration motor. I decided to use a push-button rather than a switch so that they are only active when touched/pushed.

Limpet push-button